The present invention relates to apparatus for the production of articles, for example, tubular containers where a rotary work table moves a shaping mandril or mandrils through a plurality of work stations where the forming steps are sequentially carried out during dwell periods in the work table's rotation. The present invention has for its chief object the shortening of the dwell periods of the work table to the shortest possible time to thereby increase the productive capacity of the equipment.
In known arrangements for the production of articles such as tubular containers, a rotary table which carries a plurality of support elements such as a plurality of mandrils is indexed to move the mandrils through a plurality of work stations. At each work station a forming or assembly tool is located which is timed to move into a working position after the rotary table is indexed to bring a new mandril carrying a work piece to the work station. The rotary table is then put in a dwell mode while the tools at the various stations perform their manufacturing steps in the predetermined sequence.
It has long been known that the dwell period or cycle time for the operating or manufacturing steps must be selected to take into account the particular operating step which requires the greatest time expenditure. As an example, where welding is effected at one of the stations, sufficient dwell time must be provided to allow the work piece to cool sufficiently prior to indexing or moving the table to shift the work pieces to the subsequent manufacturing step. Where the work pieces consist of plastic materials that tend to stick when heated, the cooling step has, in some circumstances, resulted in considerable slowdown of the work table resulting in an undesirable increase in the manufacturing costs.
According to the present invention, an improved apparatus is provided where the dwell time of the rotary conveyor is substantially reduced thus increasing the productive capacity of the apparatus.
This object is attained by mounting at each position of the rotary conveyor at least some of the elements of the tool members that require the greatest time expenditure so that these tool members can be moved with the particular work piece through several work stations of the conveyor and mounting devices are employed to carry these tool members so that they will be out of the area of operation of the remaining tools of the sequence when the rotary conveyor moves through other work stations of the manufacturing process.
With this arrangement, an extended number of manufacturing steps may be distributed over several work positions or stations through which the rotary conveyor moves whereby the dwell or cadence time may be set to correspond to the dwell time needed for the shorter operating steps.
According to a preferred embodiment, a plurality of forming mandrils are mounted on a rotary table which rotates about an axis to move the mandrils through a plurality of work stations. The manufacturing process commences with the mounting of, for example, one element of a container on a mandril which is then moved to a second work station where the mandril receives another component of the container. At a third work station a forming step is employed to pre-shape the elements, while at a fourth work station, a mold member and a welding mechanism are connected to the joined containers to effect sealing thereof. At a fifth work station cooling of the welded joint is permitted, while at a sixth work station, the mold member is removed. At a seventh work station a container closure is attached to the thus formed container, while at an eighth and final station, the container is removed from the rotary conveyor. Since the welding and cooling steps take a longer time than the prior and succeeding manufacturing steps, according to the present invention, in several manufacturing applications, elements of the mold member and welding tool may be permanently mounted adjacent each mandril of the rotary conveyor so as to be pivotable from a non-working to an operating or working position. To effect this movement, a cam disc is fixed about the axis of the table and the welding tool which may include the mold and a high frequency coil is mounted on arms which are pivotably secured to the table adjacent each mandril and a cam follower is attached to the pivoting arms whereby rotation of the table through the selected work stations will effect movement of the welding tool adjacent each mandril at a selected station into an operating position and then at a subsequent work station out of the operating position to permit subsequent tools at other stations to perform their operations without interference from the welding tool.
In the description that follows, a specific example of a tubular container such as is commonly used for toothpaste, cosmetics, medicines, or the like, is given but it will be understood that other types of manufacturing processes can usefully employ the principles of the present invention.